In recent years, the importance of critical analysis of the efficacy of various methods of cancer treatment has received much emphasis. The necessity of comparing like situations has lead to the development of controlled clinical trials. Because of the necessity to have large numbers of patients for proper statistical comparison and the difficulty of realizing these numbers within individual centers, it has become necessary to form groups in which various centers pool material. The Radiation Therapy Oncology Group has been formed to assess the efficacy of radiation therapy in the treatment of various malignancies using various techniques or in combination with other forms of cancer treatment. Treatment protocols are under constant professional analysis by the physicians of the group with supervision and help from the biostatistical center. The quality of radiation therapy is monitored by the Radiologic Physics Center. In addition to the analysis of treatment methods and results, information to be obtained will include a long term review of the complications of radiation and the establishment of an information center for analyzing the results of radiation therapy in rare tumors and using unusual techniques. New York University Medical Center has been a full member of the Group since 1973. BIBLIOGRAPHIC REFERENCES: Carella, RJ, Pay, N, Newall, J, Farina, AT, Kricheff, II and Cooper, JS: Computerized (Axial) Tomography in the Serial Study of Cerebral Tumors Treatment Radiation: A Preliminary Report. CANCER 37:2719-2728, June 1976. Pay, N., Carella, RJ, Lin J and Kricheff, II: The Usefulness of Computerized Tomography (CT) in Neurosurgery Patients Undergoing Radiation Therapy. Radiology 121-79-83, October 1976.